netdev - RE: [EXT] Re: [PATCH net-next 07/10] qed*: Add iWARP 100g support

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Date:   Thu, 2 May 2019 20:38:56 +0000
From:   Michal Kalderon <mkalderon@...vell.com>
To:     Leon Romanovsky <leon@...nel.org>
CC:     David Miller <davem@...emloft.net>,
        Ariel Elior <aelior@...vell.com>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH net-next 07/10] qed*: Add iWARP 100g support

> From: Leon Romanovsky <leon@...nel.org>
> Sent: Thursday, May 2, 2019 3:31 PM
> 
> On Thu, May 02, 2019 at 12:10:39PM +0000, Michal Kalderon wrote:
> > > From: Leon Romanovsky <leon@...nel.org>
> > > Sent: Thursday, May 2, 2019 8:13 AM
> > > On Wed, May 01, 2019 at 08:35:22PM -0400, David Miller wrote:
> > > > From: Michal Kalderon <michal.kalderon@...vell.com>
> > > > Date: Wed, 1 May 2019 12:57:19 +0300
> > > >
> > > > > diff --git a/drivers/infiniband/hw/qedr/main.c
> > > > > b/drivers/infiniband/hw/qedr/main.c
> > > > > index d93c8a893a89..8bc6775abb79 100644
> > > > > --- a/drivers/infiniband/hw/qedr/main.c
> > > > > +++ b/drivers/infiniband/hw/qedr/main.c
> > > > > @@ -52,6 +52,10 @@ MODULE_DESCRIPTION("QLogic 40G/100G
> ROCE
> > > > > Driver");  MODULE_AUTHOR("QLogic Corporation");
> > > > > MODULE_LICENSE("Dual BSD/GPL");
> > > > >
> > > > > +static uint iwarp_cmt;
> > > > > +module_param(iwarp_cmt, uint, 0444);
> > > MODULE_PARM_DESC(iwarp_cmt, "
> > > > > +iWARP: Support CMT mode. 0 - Disabled, 1 - Enabled. Default:
> > > > > +Disabled");
> > > > > +
> > > >
> > > > Sorry no, this is totally beneath us.
> > >
> > > It is not acceptable for RDMA too.
> >
> > Dave and Leon,
> >
> > This is a bit of a special case related specifically to our hardware.
> > Enabling iWARP on this kind of configuration impacts L2 performance.
> > We don't want this to happen implicitly once the rdma driver is loaded
> > since that can happen automatically and could lead to unexpected behavior
> from user perspective.
> > Therefore we need a way of giving the user control to decide whether
> > they want iWARP at the cost of L2 performance degradation.
> > We also need this information as soon as the iWARP device registers, so
> using the rdma-tool would be too late.
> >
> > If module parameter is not an option, could you please advise what would
> be ok ?
> > ethtool private flags ?
> > devlink ?
> 
> Yes, devlink params are modern way to have same functionality as module
> parameters.
> 
> This patch can help you in order to get a sense of how to do it.
> https://lore.kernel.org/patchwork/patch/959195/
> 
Thanks Leon, 
Michal

> Thanks
> 
> >
> > thanks,
> > Michal
> >
> > >
> > > Also please don't use comments inside function calls, it complicates
> > > various checkers without real need.
> > > dev->ops->iwarp_set_engine_affin(dev->cdev, true /* reset */);
> > >                                                 ^^^^^^^^^^^^^^
> > > Thanks